I used ohlcSeries to draw the candlestick chart but I can't update the datasets. So, how to update the datasets of candlestick chart?

For another Line chart. I used TimeSeries to draw. There is a method AddOrUpdate() to update the dataset and I can also remove the timeseries by clear() whether there is no such methods for ohlcSeries.

There are two dataset implementations you can use for the OHLC charts : DefaultOHLCDataset and OHLCSeriesCollection. The former doesn't provide any facilities to update the data, whereas the latter at least allows you to add and remove data items. It is an area that could do with some improvement.